The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those interested in science learn about the theory of evolution and how it is incorporated throughout all fields of scientific research.
This site provides a range of sources for students, teachers, and general readers on evolution. 에볼루션 바카라 체험 contains important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is seen in a variety of spiritual traditions and cultures as a symbol of unity and love. It also has important practical applications, like providing a framework to understand the evolution of species and how they react to changes in environmental conditions.
Early attempts to describe the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on the sampling of different parts of living organisms, or short DNA fragments, greatly increased the variety of organisms that could be included in a tree of life2. 무료 에볼루션 are largely composed by eukaryotes, and bacterial diversity is vastly underrepresented3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees using molecular techniques such as the small subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is a lot of diversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are typically only present in a single specimen5. A recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a large number of archaea, bacteria and other organisms that have not yet been isolated, or the diversity of which is not thoroughly understood6.
The expanded Tree of Life can be used to assess the biodiversity of a specific region and determine if particular habitats require special protection. The information is useful in a variety of ways, such as finding new drugs, fighting diseases and improving crops. This information is also extremely valuable in conservation efforts. It helps biologists discover areas that are likely to be home to species that are cryptic, which could have vital metabolic functions, and could be susceptible to the effects of human activity. While funds to protect biodiversity are essential, the best method to preserve the biodiversity of the world is to equip more people in developing countries with the information they require to act locally and promote conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between organisms. Scientists can create an phylogenetic chart which shows the evolution of taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny is essential in understanding evolution, biodiversity and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits are either analogous or homologous. Homologous characteristics are identical in their evolutionary paths. Analogous traits might appear similar however they do not have the same origins. Scientists group similar traits into a grouping known as a Clade. For instance, all the species in a clade have the characteristic of having amniotic eggs and evolved from a common ancestor that had eggs. A phylogenetic tree is then constructed by connecting the clades to identify the organisms which are the closest to each other.
To create a more thorough and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to establish the relationships between organisms. This information is more precise than morphological information and provides evidence of the evolutionary history of an individual or group. The use of molecular data lets researchers identify the number of species that share the same ancestor and estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors that include the phenotypic plasticity. This is a kind of behaviour that can change in response to particular environmental conditions. This can cause a characteristic to appear more similar to a species than another, obscuring the phylogenetic signals. However, this issue can be solved through the use of methods such as cladistics which combine analogous and homologous features into the tree.
Furthermore, phylogenetics may help predict the duration and rate of speciation. This information can assist conservation biologists make decisions about which species to protect from the threat of extinction. In the end, it is the conservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The main idea behind evolution is that organisms change over time due to their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could evolve according to its own requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that are passed on to the next generation.
In the 1930s & 1940s, concepts from various fields, including natural selection, genetics & particulate inheritance, came together to form a modern evolutionary theory. This explains how evolution is triggered by the variation in genes within the population, and how these variants change with time due to natural selection. This model, which is known as genetic drift, mutation, gene flow, and sexual selection, is a key element of the current evolutionary biology and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species through genetic drift, mutation, and reshuffling of genes during sexual reproduction, as well as through the movement of populations. These processes, as well as other ones like directionally-selected selection and erosion of genes (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time, as well as changes in the phenotype (the expression of genotypes within individuals).
Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny as well as evolution. In a recent study by Grunspan et al. It was found that teaching students about the evidence for evolution boosted their understanding of evolution in a college-level course in biology. To find out more about how to teach about evolution, look up The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species, and observing living organisms. But evolution isn't a thing that happened in the past. It's an ongoing process, that is taking place right now. Bacteria transform and resist antibiotics, viruses evolve and escape new drugs and animals alter their behavior in response to a changing planet. The changes that result are often evident.
It wasn't until the late 1980s that biologists began to realize that natural selection was also at work. The main reason is that different traits can confer an individual rate of survival and reproduction, and can be passed down from one generation to the next.
In the past, if one particular allele--the genetic sequence that controls coloration - was present in a population of interbreeding organisms, it could quickly become more prevalent than all other alleles. In time, this could mean that the number of black moths within the population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples of each are taken regularly and more than fifty thousand generations have been observed.
Lenski's research has shown that a mutation can dramatically alter the efficiency with which a population reproduces--and so, the rate at which it evolves. It also demonstrates that evolution takes time--a fact that many find hard to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in areas that have used insecticides. That's because the use of pesticides creates a pressure that favors those with resistant genotypes.
The rapid pace at which evolution takes place has led to a growing awareness of its significance in a world that is shaped by human activity, including climate change, pollution and the loss of habitats that prevent many species from adjusting. Understanding 무료 에볼루션 will help us make better decisions about the future of our planet and the lives of its inhabitants.